So I've made a character based on burrowing and a rules question has arisen that affects the overall build of my character. Keeping it simple.

I want to attack with a power that lets me shift afterwards, or push the enemy. Minor action activate my hengeyokia burrowing. Move action burrow down, not provoking from the first square since no longer adjacent. Burrow under, but end my movement directly beneath a square of "open air", as in the square above me is not underground. Make a stealth check (since neither I nor anyone else draw LoS or LoE to me as I'm burrowed and it's blocking terrain). The following turn, starting off I'd like to spend a minor action to "shut off" my hengeyokai burrowing, meaning I no longer have a burrow speed, while i'm still in the dirt with the "open air space" above me. I want to use a rogue power that lets me move first as part of the attack and then attack with sneak attack.

Question is, do I need a burrow speed to "exit" a "dirt space" and enter an "open air space"? There's not many rules AT ALL about burrowing whatsoever, and with Hengeyokai they introduced it as something PCs can get. My logic is that in normal movement you enter difficult terrain for 2 because it's... difficult, and exit it normally because the square your'e entering is just normal. If you had Forest Walk and stepped into a bush it'd cost you 1, but if you lost Forest Walk after you'd entered, you could still step out for 1, because it's a normal space.

In my head I can draw a multitude of reasons to justify it working, but I'd like to know the legit ruling on it.

First off, if you move out of a threatened square you are going to provoke regardless.

So this situation.

Starting here:XXXXXXYXXEXXXXXX

Ending here:

XXXXXXXXXEXXXYXX

Y= youE = Enemy

If you burrow out of that starting point without shifting, you will provoke and OA from E when you leave the square. Now being an Hengeyokai (Badger) gives you a burrow speed. But you cannot shift while burrowing, so I'm not sure what you are going to do to avoid getting OAed when you leave the sqaure.

Ok, all that said, lets move to the next point.

Remember your burrow speed is equal to half your speed, so you are going to be moving quite slowly. You also can't Burrow-shift with any power that lets you shift (and there are a lot of powers that let you do so).

If you are burrowing out of a square next to open air, things have LoS and LoE to you. They only don't have that if there is space between you. In the above diagram the enemy has LoS and LoE to you both times. When you pop out of your hole you will also provoke (as he will be threatening your square). A DM might rule that you have cover here, which is fair, but you won't have superior cover (which is what you need to make a stealth check to become hidden) if you have "open air" above you.

As far as leaving that square, you will not need any sort of special speed as long as you enter the surface and it won't cost any extra sqaures of movement. Remember, however, that you will provoke if you don't shift.

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If you are burrowing out of a square next to open air, things have LoS and LoE to you. They only don't have that if there is space between you. In the above diagram the enemy has LoS and LoE to you both times. When you pop out of your hole you will also provoke (as he will be threatening your square). A DM might rule that you have cover here, which is fair, but you won't have superior cover ....

Excellent wrap-up on the rest, but this point is open to contention unless there was a ruling somewhere I don't know of. While you are in the "below ground square," creatures do not have LOE to you, and barring tremorsense or XRay vision wouldn't have LOS either. Since the timing (interrupt)of any provoked OA would happen while you are still underground, there would be no risk of OA.

If the OA is allowed, it leads to the odd situtation where a fighter may hit a creature he did not have LOS or LOE to (or even an attack penalty for cover) and prevent it from emerging from the ground in the first place. It breaks versimillitude even worse with Polearm Momentum Gamble =)

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If you're in blocking terrain while burrowed, things in general will not have LoS or LoE. Blocking terrain in this case includes things like the ground.

Leaving the ground is almost always safe, for this reason. Yes, you provoke, but the OA happens while you're still in the square you're leaving, not the square you're going to, so you're still under the ground when the OA happens. And without LoE, the OA will fail. Lack of LoS will also cause it to fail.

In three dimensions, squares are cubes. Yes, there is a square below the square you're in when you're standing on the ground, and moving into that square costs one square of movement.

Yes, you provoke, but the OA happens while you're still in the square you're leaving, not the square you're going to, so you're still under the ground when the OA happens.

No you do not provoke an opportunity attack in this case because triggering the opportunity attack power is referred to as provoking an opportunity attack and in this case the opportinity attack's trigger is not met since the burrowing creature is not an enemy that you can see when it moves. (RC 246)

If you come up next to the person you have created a space that the creature can see into, and probably fit through (see the tunneling rules). Which means that you are effectively in a sqaure 1 down, but still in the open air. So they can still see you. You might get cover from a hard corner, but thats it.

Now, those sqaures were you are burrowing under him, yes you don't provoke. No LoE, no LoS, you are burrowed. But when you go in initially, and when you pop out the other side, you are visible on both sides. So you will provoke.

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If you come up next to the person you have created a space that the creature can see into, and probably fit through (see the tunneling rules). Which means that you are effectively in a sqaure 1 down, but still in the open air. So they can still see you. You might get cover from a hard corner, but thats it.

Now, those sqaures were you are burrowing under him, yes you don't provoke. No LoE, no LoS, you are burrowed. But when you go in initially, and when you pop out the other side, you are visible on both sides. So you will provoke.

Depends more on real world physics than the rules. By the rules, you're down a square and out of LoS.

You are down a sqaure and out of LoS if you are no longer burrowing in a tunneled square next to an enemy? That seems very... I don't have a good word for it. Would someone else who went into that sqaure after you left be out of LoS since they are in the tunneled square? What about someone standing on top of the tunneled sqaure?

I feel like the part of the rules that go over this are vague, but the tunneling bit seems to suggest that when you create something through burrowing that it should function like a normal passageway for something of your size (So, shouldnt block LoS or LoE unless you have a solid square of something between them.

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You only leave a space behind you if you have the Tunneling feature. Otherwise it is as if you were never there, you don't leave a hole behind at all. And I don't think there are any ways for a PC to get Tunneling either.

You only leave a space behind you if you have the Tunneling feature. Otherwise it is as if you were never there, you don't leave a hole behind at all. And I don't think there are any ways for a PC to get Tunneling either.

See now thats an important distinction, and one I didn't notice. So with no tunneling, there is no tunnel.

But by the same note if he doesn't have a burrow speed can he not leave the sqaure? The example was that he would turn off his burrow speed so that hey could shift or move out of the hole. I would think if he ends not on the surface he cannot end his burrowing speed at all. Correct?

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I don't think you can burrow through earth without a burrowing movement mode. Another akward thing about the OP's scenario is that since the badger's burrowing movement mode doesn't have the tunneling trait, how does it go from a tiny size to a medium one while still occupying an untunneled tiny space if squeezing doesn't happen automatically but require an action ?

EDIT Found the answer. Nature's Mask would fail according to how Polymorph works, and leave the PC stunned.

RC 119 Changing Size: If a polymorph effect would make a creature too large to fit in the available space, the effect fails against the creature, but it is stunned (save ends).

I don't think you can burrow through earth without a burrowing movement mode. Another akward thing about the OP's scenario is that since the badger's burrowing movement mode doesn't have the tunneling trait, how does it go from a tiny size to a medium one while still occupying an untunneled tiny space if squeezing doesn't happen automatically but require an action ?

EDIT Found the answer. Nature's Mask would fail according to how Polymorph works, and leave the PC stunned.

RC 119 Changing Size: If a polymorph effect would make a creature too large to fit in the available space, the effect fails against the creature, but it is stunned (save ends).

So in the OP's scenario he would gain burrowing speed, move underground, provoke an OA, move next to the target, lose burrowing speed while not in a tunnel (no tunneling), not be able to fit in the sqaure and become stunned (Save Ends)? I feel like that is slightly different than he intended...

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